In this book we are concerned with the most fundamental event of our times—the enormous growth of the world's population during the last 3 decades, and the prospects for continued growth in the future. Many people believe, as Malthus did at first, though he later changed his mind, that the numbers of human beings will always increase up to a level set by the available food supply, or by enemies and disease. "Gigantic, inevitable famine stalks in the rear of misery and vice to limit the numbers of mankind." Even though death rates today are lower than they have ever been, and the proportion of the world's human population that is seriously malnourished is probably less than at any time since the Old Stone Age, the belief is widespread that uncontrolled population growth in the earth's poor countries is leading to catastrophe. It is possible, however, to take a different view, based on what we know about the history of human populations and on the behavior of many people at the present time—a view that social inventions will lead to a deliberate limitation of fertility by individual couples. At the same time the technical potentialities exist, not only to feed all human beings, but greatly to improve the quality of human diets, at least until the end of this century. During the next 20 years no change in human fertility patterns can have much effect on the dimensions of the world food problem. And the natural resources available to present technology are sufficient to allow a vast improvement in the standard of living of all the people who will inhabit the earth 20 to 30 years from now. This is not to say that such an improvement in diets or standard of living will inevitably occur. It will depend on the improvement of social and economic institutions, and on the growth of cooperation and interdependence among the peoples of the world. Nevertheless, a reduction in present rates of population growth is highly desirable from many points of view, becausjjjijjjb-.^^ tion growthjiaye seriously^adverse social and economicjjffects. A reduction in human fertility is an important"componenFbT"soclal and economic development, although such a reduction cannot be a substitute for large capital investments and massive transfers of technology.w, based on the available evidence and the need to d< thing with the tools at our disposal to improve the conditions of families, by giving parents the means and the incentives to limit their 1 and to help societies balance their numbers with available food, jobs tion, health services, or resources.